Synthesis and characterization of some Mn(II) and Mn(III) complexes of N, N′- o-phenylenebis(salicylideneimine)(LH 2) and N, N′- o-phenylenebis(5-bromosalicylideneimine)(L′H 2). Crystal structures of [Mn(L)(H 2O)(ClO 4)], [Mn(L)(NCS)] and an infinite linear chain of [Mn(L)(OAc)]

• Published in: Inorganica Chimica Acta 2005-05, Vol.358 (8), p.2473-2481
• Main Authors: Biswas, Subhendu, Mitra, Kamala, Schwalbe, C.H., Robert Lucas, C., Chattopadhyay, Shyamal K., Adhikary, Bibhutosh
• Format: Article
• Language: English
• Subjects: Acetate bridged manganese(III) chain; Electrochemistry; Electronic spectra; Manganese(II) and manganese(III) complexes; N 2O 2 donors; Phenolate Schiff bases; X-ray structure
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2005.01.026

A series of manganese(II) and manganese(III) complexes of formulae [Mn(L)] and [Mn(L)(X)], respectively (X = ClO 4, OAc, NCS, N 3, Cl, Br and I); L = N, N′- o-phenylenebis(5-Y-salicylideneimine) (Y = H, Br) have been synthesized. The X-ray structures show that the manganese(III) is six coordinated in 3 and 5 coordinated in 13, there is an infinite chain of the Mn(L) moieties bridged by acetate ions in 5. A series of manganese(II) [Mn(L)] and manganese(III) [Mn(L)(X)] (X = ClO 4, OAc, NCS, N 3, Cl, Br and I) complexes have been synthesized from Schiff base ligands N, N′- o-phenylenebis(salicylideneimine)(LH 2) and N, N′- o-phenylenebis(5-bromosalicylideneimine)(L′H 2) obtained by condensation of salicylaldehyde or 5-Br salicylaldehyde with o-phenylene-diamine. The complexes have been characterized by the combination of IR, UV–Vis spectroscopy, magnetic measurements and electrochemical studies. Three manganese(III) complexes 3 [Mn(L)(ClO 4)(H 2O)], 5 [Mn(L)(OAc)] and 13 [Mn(L)(NCS)] have been characterized by X-ray crystallography. The X-ray structures show that the manganese(III) is hexa-coordinated in 3, it is penta-coordinated in 13, while in 5 there is an infinite chain where the MnL moieties are connected by acetate ions acting as bridging bidentate ligand. The cyclic voltammograms of all the manganese(III) complexes exhibit two reversible/quasi-reversible/irreversible responses assignable to Mn(III)/Mn(II) and Mn(IV)/Mn(III) couples. It was observed that the ligand L′H 2 containing the 5-bromosal moiety always stabilizes the lower oxidation states compared to the corresponding unsubstituted LH 2. Cyclic voltammograms of the manganese(II) complexes ( 1 and 2) exhibit a quasi-reversible Mn(III)/Mn(II) couple at E 1/2 −0.08 V for 1 and 0.054 V for 2.